The invention pertains to a system and method for removing a thigh bone from a defeathered whole leg poultry product.
Poultry thigh meat is a generally high quality, tasty meat type that is highly valued by consumers. With the increased popularity of this type of poultry meat, the demand for boneless poultry thigh meat also increases.
In automated poultry processing plants, carcass parts are preferably processed while they are arranged in, on or at product carriers that bring the carcass parts to the processing stations in which the processing can take place. These carriers generally engage the carcass part by the legs in the vicinity of the tarsal joints, such that the carcass or carcass part is suspended from the carrier.
When it comes to removing the thigh bone in order to obtain boneless thigh meat, in automated poultry processing plants this preferably takes place while the drumstick is still connected to the thigh. The combination of the drumstick and thigh is called “whole leg poultry product”, even though the part of the leg from the tarsal joint to the foot and the foot itself have generally already been removed. The advantage of this is that the whole leg poultry product may be in a standard carrier during the thigh bone removal process, optionally even in the same carrier in which the carcass or carcass part was at the beginning of the process of dividing a chilled and eviscerated carcass into carcass parts. This means that transfer to a different carrier, either automatically or manually, can be reduced or even avoided.
WO00/59311 discloses two ways of removing the thigh bone from a whole leg poultry product while the whole leg product is engaged by its tarsal joint. However, it should be noticed that in this disclosure, the whole leg poultry product is no longer in a standard carrier (e.g. a standard division line carrier) when the thigh bone removal process is carried out. It has been transferred form such a standard carrier to a special, dedicated product support.
In the first method of removing the thigh bone that is disclosed in WO00/59311, a transverse cut is made at the knee joint, to sever the thigh bone and the drumstick bone from each other. Also, a longitudinal cut is made in the thigh meat, to expose the thigh bone. Then, the thigh bone is severed from the thigh meat between the knee joint and the hip joint end of the thigh bone by pulling the thigh bone sideways out of the thigh meat via the longitudinal cut in the thigh meat. During this pulling, the thigh meat remains connected to the hip side end of the thigh bone, so the thigh bone is more or less rotated about its hip side end. Then, as a final step, the connection between in the thigh meat and the thigh bone at the hip side end of the thigh bone is cut through.
It has been found that when carrying out this method, it is very hard to make the longitudinal cut in the thigh meat at the right location without cutting into the drumstick as well. Cutting into the drumstick is generally undesired, as the drumsticks are desired to have undamaged skin thereon. Also, the depth of the longitudinal cut in the thigh meat has to be very precise. If cut too deep, bone splinters may be found in the thigh meat and if cut too shallow, the thigh bone cannot be removed properly.
In the second method of removing the thigh bone that is disclosed in WO00/59311, the drumstick bone and the thigh bone remain connected to each other, but the thigh meat and the drumstick meat are severed from each other. In this method, then the thigh meat is scraped from the thigh bone in the direction from the knee joint to the hip side end of the thigh bone. In this method, quite a high pulling force is exerted on the tissues that connect the drumstick bone and the thigh bone, in particular when the thicker ends of the thigh bone, the condyles, pass through the scraper. There is a significant chance that the connection between the drumstick bone and the thigh bone breaks during the scraping, in particular when the connection has been damaged already somewhat when the thigh meat and the drumstick meat were severed. If the connection between the drumstick bone and the thigh bone breaks during the scraping, the thigh bone will not be removed from the thigh meat.
NL1001226 discloses a manual method for removing the thigh bone from a poultry thigh. In this manual method, a first incision is made in the lengthwise direction of the thigh, from the knee joint to the hip joint. Then a second incision is made in the knee joint, in a direction that is generally transverse to the longitudinal direction of the thigh bone. After these incisions are made, the thigh bone is removed by rotating the thigh bone sideways around the hip joint, by which rotation the thigh bone is taken out of the thigh meat via the first incision, which extends from the knee joint to the hip joint.